Generally, a transparent conductive layer is used as an essential component of electric and electronic devices such as a power source in display devices, an electromagnetic wave shielding film in home appliances, a transparent electrode in various display fields such as a liquid crystal display (LCD), an organic light emitting diodes (OLED), a field emission display (FED), a plasma display panel (PDP), a flexible display, an electronic paper, or the like.
Currently, as a material of the transparent conductive layer, a conductive inorganic oxide material such as indium-tin oxide (ITO), antimony-tin oxide (ATO), antimony-zinc oxide (AZO), or the like, is mainly used.
The transparent conductive layer having relatively high conductivity and transmittance may be prepared using the material by a sputtering method, an ion beam method, a vacuum deposition method, or the like, that are generally used. However, in this method, cost for equipment investment is high, and it is difficult to mass-produce the transparent conductive layer and prepare a large size transparent conductive layer. Particularly, this method has a limitation in a transparent substrate requiring a low temperature process, such as a plastic film. At the time of deposition by the sputtering method, composition of the transparent conductive layer may be changed according to the conditions such as oxygen partial pressure, a temperature, and the like, and the transmittance and resistance of the thin film may be rapidly changed. In addition, even after the process is completed, a crack may be generated in the thin film, which increases the resistance. Therefore, a method for preparing a transparent conductive layer performed by coating a film using a wet coating method such as a spin coating method, a spray coating method, a dip coating method, a printing method, or the like, that are appropriate for low cost and a large size and then firing the coating film, or the like, has been suggested. For example, a transparent conductive layer using a metal fine particle and a binder is disclosed in Korean Patent Laid-Open Publication No. 1999-011487, a composition for a transparent conductive layer in which a hollow carbon nano fiber is added to tin oxide is disclosed in Korean Patent Laid-Open Publication No. 1999-064113, and a coating solution for a transparent conductive light selectively absorbing film in which neodymium oxide is added to tin oxide or indium oxide was disclosed in Korean Patent Laid-Open Publication No. 2000-009405. In addition, a method for manufacturing a solution for a transparent conductive layer containing a metal particle such as gold, silver, or the like, is disclosed in Japanese Patent Laid-open Publication No. 2003-213441.
A surface resistance of the transparent conductive layer prepared by the above-mentioned methods is high, that is, about 103 to 104Ω/□, time-dependent changes, an increase in the surface resistance according to the change in surroundings and time, or the like, are generated therein, such that initial conductivity may not be maintained. Therefore, this transparent conductive layer has a limitation in being used as the transparent conductive layer.